1 /* Copyright (C) 2003, 2004, 2006, 2007 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
23 #include <lowlevellock.h>
27 #include <shlib-compat.h>
30 struct _condvar_cleanup_buffer
34 pthread_mutex_t
*mutex
;
40 __attribute__ ((visibility ("hidden")))
41 __condvar_cleanup (void *arg
)
43 struct _condvar_cleanup_buffer
*cbuffer
=
44 (struct _condvar_cleanup_buffer
*) arg
;
45 unsigned int destroying
;
46 int pshared
= (cbuffer
->cond
->__data
.__mutex
== (void *) ~0l)
47 ? LLL_SHARED
: LLL_PRIVATE
;
49 /* We are going to modify shared data. */
50 lll_lock (cbuffer
->cond
->__data
.__lock
, pshared
);
52 if (cbuffer
->bc_seq
== cbuffer
->cond
->__data
.__broadcast_seq
)
54 /* This thread is not waiting anymore. Adjust the sequence counters
55 appropriately. We do not increment WAKEUP_SEQ if this would
56 bump it over the value of TOTAL_SEQ. This can happen if a thread
57 was woken and then canceled. */
58 if (cbuffer
->cond
->__data
.__wakeup_seq
59 < cbuffer
->cond
->__data
.__total_seq
)
61 ++cbuffer
->cond
->__data
.__wakeup_seq
;
62 ++cbuffer
->cond
->__data
.__futex
;
64 ++cbuffer
->cond
->__data
.__woken_seq
;
67 cbuffer
->cond
->__data
.__nwaiters
-= 1 << COND_NWAITERS_SHIFT
;
69 /* If pthread_cond_destroy was called on this variable already,
70 notify the pthread_cond_destroy caller all waiters have left
71 and it can be successfully destroyed. */
73 if (cbuffer
->cond
->__data
.__total_seq
== -1ULL
74 && cbuffer
->cond
->__data
.__nwaiters
< (1 << COND_NWAITERS_SHIFT
))
76 lll_futex_wake (&cbuffer
->cond
->__data
.__nwaiters
, 1, pshared
);
81 lll_unlock (cbuffer
->cond
->__data
.__lock
, pshared
);
83 /* Wake everybody to make sure no condvar signal gets lost. */
85 lll_futex_wake (&cbuffer
->cond
->__data
.__futex
, INT_MAX
, pshared
);
87 /* Get the mutex before returning unless asynchronous cancellation
89 __pthread_mutex_cond_lock (cbuffer
->mutex
);
94 __pthread_cond_wait (cond
, mutex
)
96 pthread_mutex_t
*mutex
;
98 struct _pthread_cleanup_buffer buffer
;
99 struct _condvar_cleanup_buffer cbuffer
;
101 int pshared
= (cond
->__data
.__mutex
== (void *) ~0l)
102 ? LLL_SHARED
: LLL_PRIVATE
;
104 /* Make sure we are along. */
105 lll_lock (cond
->__data
.__lock
, pshared
);
107 /* Now we can release the mutex. */
108 err
= __pthread_mutex_unlock_usercnt (mutex
, 0);
109 if (__builtin_expect (err
, 0))
111 lll_unlock (cond
->__data
.__lock
, pshared
);
115 /* We have one new user of the condvar. */
116 ++cond
->__data
.__total_seq
;
117 ++cond
->__data
.__futex
;
118 cond
->__data
.__nwaiters
+= 1 << COND_NWAITERS_SHIFT
;
120 /* Remember the mutex we are using here. If there is already a
121 different address store this is a bad user bug. Do not store
122 anything for pshared condvars. */
123 if (cond
->__data
.__mutex
!= (void *) ~0l)
124 cond
->__data
.__mutex
= mutex
;
126 /* Prepare structure passed to cancellation handler. */
128 cbuffer
.mutex
= mutex
;
130 /* Before we block we enable cancellation. Therefore we have to
131 install a cancellation handler. */
132 __pthread_cleanup_push (&buffer
, __condvar_cleanup
, &cbuffer
);
134 /* The current values of the wakeup counter. The "woken" counter
135 must exceed this value. */
136 unsigned long long int val
;
137 unsigned long long int seq
;
138 val
= seq
= cond
->__data
.__wakeup_seq
;
139 /* Remember the broadcast counter. */
140 cbuffer
.bc_seq
= cond
->__data
.__broadcast_seq
;
144 unsigned int futex_val
= cond
->__data
.__futex
;
146 /* Prepare to wait. Release the condvar futex. */
147 lll_unlock (cond
->__data
.__lock
, pshared
);
149 /* Enable asynchronous cancellation. Required by the standard. */
150 cbuffer
.oldtype
= __pthread_enable_asynccancel ();
152 /* Wait until woken by signal or broadcast. */
153 lll_futex_wait (&cond
->__data
.__futex
, futex_val
, pshared
);
155 /* Disable asynchronous cancellation. */
156 __pthread_disable_asynccancel (cbuffer
.oldtype
);
158 /* We are going to look at shared data again, so get the lock. */
159 lll_lock (cond
->__data
.__lock
, pshared
);
161 /* If a broadcast happened, we are done. */
162 if (cbuffer
.bc_seq
!= cond
->__data
.__broadcast_seq
)
165 /* Check whether we are eligible for wakeup. */
166 val
= cond
->__data
.__wakeup_seq
;
168 while (val
== seq
|| cond
->__data
.__woken_seq
== val
);
170 /* Another thread woken up. */
171 ++cond
->__data
.__woken_seq
;
175 cond
->__data
.__nwaiters
-= 1 << COND_NWAITERS_SHIFT
;
177 /* If pthread_cond_destroy was called on this varaible already,
178 notify the pthread_cond_destroy caller all waiters have left
179 and it can be successfully destroyed. */
180 if (cond
->__data
.__total_seq
== -1ULL
181 && cond
->__data
.__nwaiters
< (1 << COND_NWAITERS_SHIFT
))
182 lll_futex_wake (&cond
->__data
.__nwaiters
, 1, pshared
);
184 /* We are done with the condvar. */
185 lll_unlock (cond
->__data
.__lock
, pshared
);
187 /* The cancellation handling is back to normal, remove the handler. */
188 __pthread_cleanup_pop (&buffer
, 0);
190 /* Get the mutex before returning. */
191 return __pthread_mutex_cond_lock (mutex
);
194 versioned_symbol (libpthread
, __pthread_cond_wait
, pthread_cond_wait
,